In a conventional radio receiver, a complex signal pair can be generated that has an in-phase (I) component and a quadrature (Q) component. The I and Q signal components are generated by modulating the received signal with an in-phase Local Oscillator (LO) signal to generate the I component while simultaneously modulating the same received signal with a quadrature LO signal phase shifted by 90 degrees from the in-phase LO so as to generate the Q component signal. Accordingly, in a conventional receiver, the complex IQ signal pair is demodulated using two mixers; a first mixer produces the analog I signal component and a second mixer, operating at the same frequency as the first mixer and at a 90 degree phase shift, produces the analog Q signal component. The analog I and Q signal components are typically filtered, digitized, and processed to produce sampled received data. Thus, the conventional approach requires two mixers in the analog front end, one for each of the complex signal components (I and Q). Likewise, each signal component branch requires its own filtering and other processing components, and each signal component is separately digitized.
Newer radio architectures, such as Software Defined Radio (SDR) systems, are able to receive a variety of signal types over a broad range of frequencies. That is, they can receive multiple different signals simultaneously. To receive multiple complex signals conventionally requires duplication of a single complex signal receiver, each complex receiver comprising two mixers where one is phase shifted, two filters, etc. The duplication of components to receive multiple signals, of course, adds to the amount of space, power, and other resources required for implementation, in proportion to the number of received signal being simultaneously processed. Clearly it would be beneficial to reduce the number of components used in the receiver system while still facilitating the simultaneous reception of multiple varied signals. Such a reduction of components would be possible if one of the complex signal component paths could be eliminated.
Accordingly, there is a need for a method and apparatus for obtaining both the in-phase and quadrature signal components using a single front end path.
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The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.